Across the ancient Greek world there were many wars and clashes. However, there is only one who changed the course of Greek history forever; the Peloponnesian War. Caused by the growing tension between Athens and Sparta, it came and went, leaving nothing but destruction in its wake. Athens' defeat in the Peloponnesian War brought about the fall of Greece and the end of the Classical era. The roots of the Peloponnesian War date back well before 431 BCE, when it officially began. This dates back to the Persian Wars, where the Athenians found their homes burned by the hands of the Persians. This disaster left the Athenians without a home or sanctuary. Even though it was a defeated battle in the middle of a victorious war, they still had reason to believe that the Persians would return for more. Fearing that their city would be burned down again, the Athenians knew they had to do something. Naturally, they chose to get help. Gathering the neighboring city-states around them, the Athenians formed the Delian League; an alliance working directly to defend all of Greece against Persian attacks (Kagan 8). At first it worked well; everyone had a say in what happened in the league and everyone was happy. However, the Athenians understood that if they gained more power, the members of the league would not be strong enough to resist. So that’s exactly what they did; they gained more and more power until what was the Delian League became the Athenian Empire (Kagan 8). As they became even more powerful and wealthy, their neighbors in Sparta and the Peloponnesian League, Sparta's alliance, could not help but notice (Kagan 13). In 431 BCE, lit in the middle of a paper......a trail of destruction in its wake, this war changed the entire course of ancient Greek history. Although there have been countless wars in Greek history, the Peloponnesian War was certainly the most consequential. Works Cited Decarlo, Nicole. “Classical period, Greek.” Encyclopedia of World History: Ancient World. New York: Facts on File, Inc., 2008. Facts on File. February 20, 2011..Hanson, Victor Davis. The Reader's Companion to Military History. New York: HoughtonMifflin Company, 1996. Hanson, Victor Davis. The Wars of the Ancient Greeks. New York: Cassell, 1999. Kagan, Donald. The Peloponnesian War. New York: Viking, 2003. Ober, Josiah. “Peloponnesian War.” American Encyclopedia. 1998 ed. Danbury, CT:Grolier Incorporated, 1997.